Use of a novel operation strategy in constructed wetland for high strength wastewater treatment

This paper describes a research attempt to employ a novel operation strategy, i.e. the first stage anaerobic-up flow (with effluent recirculation) plus the remaining stages tidal flow, into an alum sludge-based constructed wetland system (CWs) for the purpose of enhancing the high strength wastewater treatment performance with special focuses on organics and nitrogen removal. Analysis of the system´s performance showed that tidal flow strategy enhances the oxygen transport and diffusion, improving organics and NH₄-N reduction. Effluent recirculation could further increase organics elimination by extending interaction time and benefit denitrification process. In addition, denitrification could be further enhanced by anaerobic-up flow in the first stage. Therefore, even under high organic loading of 58-146 g BOD₅/m²d, prominent performance of the system for the removals of COD (82%), BOD₅ (91%), SS (92%), NH₄-N (94%), TN (82%) and TP (95%) was achieved.